The present invention relates generally to a semiconductor component package assembly and more particularly to a semiconductor component package assembly including an integral radio frequency (RF) and electromagnetic interference (EMI) shield and its method of manufacture.
A typical integrated circuit package is comprised of (1) an IC chip including an array of chip input/output terminals, (2) means for supporting the chip, for example, either a leadframe or substrate, including an array of electrically conductive leads, (3) bonding wires electrically connecting the chip input/output terminals with respective ones of the electrically conductive leads, and (4) plastic material encapsulating the IC chip, support means and bonding wires. This overall package is typically manufactured by first supporting the IC chip on the support member. The bonding wires are then attached to electrically interconnect the input/output terminals of the IC chip to the electrically conductive leads of the support member. This subassembly is then placed in a cooperating mold to encapsulate the IC chip, support means and bonding wires in plastic.
Attention is now directed to FIG. 1, which diagrammatically illustrates an intermediate step in the production of a prior art IC package of the type described immediately above. An intermediate IC assembly, which is generally indicated by the reference numeral 10 is shown prepared for overall encapsulation. Intermediate IC assembly 10 includes an IC chip 12 including an array of chip input/output terminals 13. Chip 12 is supported on a suitable support member 14 which can be, for example, a leadframe or a dielectric substrate. The support member includes an array of electrically conductive leads 16 electrically connected to respective chip input/output terminals by an array of bonding wires 18.
Still referring to FIG. 1, a mold for use in encapsulating intermediate IC assembly 10 is generally indicated by the reference numeral 20. Mold 20 includes a runner 22 which leads from an external supply of molding material (not shown) to a mold cavity 24 for accommodating a flow of molding material 26 into mold cavity 24. A fixed gate 28 is located in runner 22 at the point where the runner enters mold cavity 26. Intermediate IC assembly 10 is supported within mold cavity 24 for overall encapsulation by the molding material. As the molding material is injected into the cavity it flows around the intermediate IC assembly including bonding wires 18, IC chip 12 and at least a portion 29 of electrically conductive leads 16 which are within the mold cavity. Bonding wires 18 are generally formed from gold and are quite frail. As molding material 26 is injected, care must be taken so as to avoid the phenomenon of wire sweep in which the bonding wires are easily disconnected or shorted together by the inflowing molding material. Following the injection of the molding material into the mold cavity, the mold material is allowed to harden whereby to form a monolithic encapsulation structure.
While the method of producing a prior art integrated circuit package, as depicted in FIG. 1, does produce an IC package which is generally satisfactory for its intended purpose, certain electronic applications such as, for example, high gain RF amplifiers require shielding for electronic components like IC 12 from extraneous electromagnetic and radio frequency noise originating from sources external to the overall component package. In other instances, shielding is required if a particular component generates radio frequency noise or electromagnetic interference at such levels that other components may be deleteriously affected or this noise may, in fact, be produced at levels in violation of, for example, FCC regulations. In the past, shielding has generally been provided in the form of an additional grounded metal enclosure external to any particular individual semiconductor component package, for example shielding an entire functionally related section of a circuit board and surrounding that portion of the latter containing the offending sensitive or noisy electronic component or components. The incorporation of such shielding, however, results in increased production and manufacturing costs and, in some cases, also results in a disadvantageous increase in the size of the overall assembly.
The present invention introduces a highly advantageous semiconductor component package assembly and its associated method of manufacture which incorporates RF/EMI shielding within a package which is no larger than functionally identical unshielded prior art packages whereby to eliminate the need for a separate grounded metal enclosure.